Ping Pong mechanism

[chuwt]

I wanner know how server send ping packet when using HTTP long-polling transport, is there a doc to show the detail?

[darrachequesne]

Hi! The documentation could indeed be more detailed on this point.

Here's what happens:

• the server sends a ping packet (a "2") on the ongoing GET request
• the client sends a pong packet back (a "3") with a POST request
• the client then opens another long-running GET request

You can take a look at the schema here: https://socket.io/docs/v4/how-it-works/#HTTP-long-polling

[chuwt]

Thanks for your reply! Do you mean:

1. client send Get request to server
2. server received and send ping packet to client
3. client received ping packet and send pong packet request with Post

[darrachequesne]

Yes that's right 👍

The GET request is a long-running request, that is left open until the server wants to send some data to the client, hence the "long-polling" name.

[chuwt]

Thanks for your patience, it's clear for me now.

[awesomelike]

@darrachequesne you said "GET request is a long-running request", how long it can be? Something like more than 60 seconds? I have a question about this here: #4076